Correct Option: A

In the 1950s, Arvid Carlsson demonstrated that dopamine was a neurotransmitter in the brain and not just a precursor fornorepinephrine, as had been previously believed. He developed a method for measuring the amount of dopamine in brain tissues and found that dopamine levels in the basal ganglia, a brain area important for movement, were particularly high. He then showed that giving animals the drug reserpine caused a decrease in dopamine levels and a loss of movement control. These effects were similar to the symptoms of Parkinson’s disease. Arvid Carlsson subsequently won the Nobel Prize in Physiology or Medicine in 2000.